Disco 2 Rough running when auto gearbox is in P or N

I'm a new member here. Will be asking questions initially, but in time I hope to contribute constructively.

I've not been lazy, I have done a search, but haven't been able to find anything.

There is a chance to buy a 2004 Discovery II Td5 auto. But it has a fault: the engine runs rough when the autobox is in Park or Neutral, it runs ok otherwise? Any ideas what may be the cause or what other information would help to diagnose the problem.

Many thanks

Steve

Just sounds like the tick-over might be a bit low, which could probably have a number of causes.
But be patient and others more in the know will come on.
At least it sounds driveable.
What is your definition of "rough"?
Have you driven the vehicle?

Just seen this exact symptom and the problem was an injector, the ECU swaps to a different fuel map with reduced fuelling for P/N exactly like on the manuals when the clutch switch is engaged and if the injectors are not in the best shape they can misbehave on that.... though there can be other issues too, a live data log is needed

Stanleysteamer said:

Just sounds like the tick-over might be a bit low, which could probably have a number of causes.
But be patient and others more in the know will come on.
At least it sounds driveable.
What is your definition of "rough"?
Have you driven the vehicle?

Click to expand...

Thanks for your reply. No, I haven’t seen it yet, where I live is in COVID-19 (Scottish) level 3, meaning I can’t travel outside my local authority area to where the vehicle is. While, when I do get to see it, I can check for chassis/body rot and mechanical (suspension/steering/axles/etc.) problems, the Td5 engine, auto gearbox and electrics are new to me, so I’m trying to learn before I buy problems.

Rough - not running smooth and cutting out.

Steve

sierrafery said:

Just seen this exact symptom and the problem was an injector, the ECU swaps to a different fuel map with reduced fuelling for P/N exactly like on the manuals when the clutch switch is engaged and if the injectors are not in the best shape they can misbehave on that.... though there can be other issues too, a live data log is needed

Click to expand...

That seems more promising and a simple fix.The seller has said a nanocom diagnostics has not shown any faults. I don’t now what nanocom diagnosis was run yet - could it give the live data log you refer to.

Do the injectors respond well to taking a bath in an ultrasonic cleaner, or is replacement the easier (but costlier) option. I read some where about putting injector codes into replacement ecu’s, would this have to be done if the injector is replaced?

The seller has indicated this happens all the time, ah well, at least it isn’t an intermittent fault (the type that frustrates me).

I’ve been reading back posts on this forum. The XYZ has come up a few times, I’ve no idea what or where the XYZ is and I can’t get from the posts anymore than it can be adjusted and the contacts can be cleaned. But then wouldn’t any faults with it be reported during the nanocom diagnosis?

I much appreciate your knowledge and willingness to share it with this Dunderhead.

Steve

The live data readings(named "inputs fuelling" on nanocom) will show if there is a missbalance between injectors at idle in P/N if that's the case and the one which is problematic(if not more of them) will have higher readings than the others. You may try with a good brand injector cleaner additive in the tank to see what happens, If you remove the injectors you have to put them back in the same places to retain the coding also the seals have to be renewed, here's a guide if you get there http://www.discovery2.co.uk/Injector Seals.html

sierrafery said:

The live data readings(named "inputs fuelling" on nanocom) will show if there is a missbalance between injectors at idle in P/N if that's the case and the one which is problematic(if not more of them) will have higher readings than the others. You may try with a good brand injector cleaner additive in the tank to see what happens, If you remove the injectors you have to put them back in the same places to retain the coding also the seals have to be renewed, here's a guide if you get there http://www.discovery2.co.uk/Injector Seals.html

Click to expand...

Thank you